Drawing and stretching press for sheet metal



Sept. 11, 1956 o. OECKL DRAWING AND STRETCHING PRESS FOR Filed Jan. a, 1955 SHEET METAL 5 Sheets-sheaf. 1

Sept. 11, 1956 o. o c 2,762,417

DRAWING AND STRETCHING PRESS FOR SHEET METAL Filed Jan. 8, 1953 5 Sheets-Sheet 2 Sept. 11, 1956 o. OECKL 2,762,417

DRAWING AND STRETCHING PRESS FOR SHEET METAL Fil'ed Jan. 8, 1953 5 Sheets-Sheet 3 Ill/V TOP Sept. 11, 1956 0. 05cm. H 2,762,417

DRAWING AND STRETCHING PRESS FOR SHEET METAL Sept. 11, 1956 o. OECKL 2,762,417

DRAWING AND STRETCHING PRESS FOR SHEET METAL Filed Jan. 8, 1953 5 Sheeis-Sheet 5 DRAWING AND srunrcrnwo PRESS FOR SHEET METAL Otto Oeckl, Kassel, Germany Application January 8, 1953, Serial No. 330,309

3 Claims. (Cl. 153-48) This invention relates to a drawing and stretching press for sheet metal with a piston carrying the tool and with two stretching and gripping devices at opposite sides of the tool.

The first object of the invention is to provide driven swinging arms of considerable length pivotally connected with their one end to the lower part of the press frame, preferably of the press cylinder, and carrying on their other free end the gripping devices so that these gripping devices perform an arclike movement when the arms swing away and towards the tool. The work piece is hereby subjected to a pull along curves which stretches the sheet horizontally and, simultaneously, draws it downwardly forcing it around the forming die or mould. These swinging arms are thus arranged and constructed to allow a great working area within their two extreme positions, swung in and swung out, so that work pieces of any desired length can be manufactured. These presses are advantageously simple in their construction and no bending stresses occur in the gripping and stretching devices as they occur in constructions known hitherto.

A further object of the invention is to use pressureactuated means for forcing the swinging arms outwardly. These means are arranged in the middle of the press between the swinging arms, preferably on the press cyl inder with their one end, and acting on the gripping devices with their other end, so that the gripping devices form the outermost circumference of the working area of the press. Thus the work piece is accessible from all sides and can be finished by laborers undisturbed by projecting parts.

Another object of the invention is to arrange the gripping devices turnably on the swinging arms, and to operate the pressure actuated means independently of each other to permit the gripping devices to be adjusted to any position parallel or inclined to the press table.

A further object of the invention is to provide in a drawing and stretching press with or without swinging arms a single central press cylinder in which a piston carrying the press table is turnable so that the table can be adjusted longitudinally or angularly by means of this turnable piston. For inclined positions the press table is provided with a plate which can be tilted by means of one or a plurality of pressure-actuated, preferably hydraulic, pistons, the cylinder of which is fixed at one side of the press table.

Another object of the invention is to provide gripping devices with continuous body and jaws extending over the whole length of the table or die, said jaws being clamped by keys which are pressed into the body of the gripping devices by power driven means, preferably hydraulically-driven means.

The invention is illustrated in the accompanying drawlugs:

Fig. 1 is a side view of a drawing and stretching press hydraulically driven, the left swinging arm being in an outward and the right arm in an inward position. Fig. 2 is a plan view of the press according to Fig. 1,

ms tent 2 ,762,417 Patented Sept. 11, 1956 ice in their drawn-in position driven by spindles, and with' the press table longitudinally adjusted.

Fig. 6 is a side view of the press according to Fig. 5 with swinging arms in a swung-out position and with the press table transversely adjusted;

Fig. 7 is a side view, on an enlarged scale, of the press table of Fig. 5, and showing one single press cylinder, a turnable piston, and a plate adjustably inclined;

Fig. 8 shows on a reduced scale diagrammatically in plan view the press table and gripping devices;

Fig. 9 is a plan view of gripping devices which may be inserted in the swinging arms of the presses according to Figs. 1-8; and

Figs. 10 and 11 show in cross section two further embodiments of gripping devices.

Corresponding and like parts are referred to in the following description and indicated in the accompanying drawings by the same reference characters.

Figs. 1-3 show the piston 2 carrying the tool and moving upward in a corresponding upright cylinder 1 under the action of a pressure fluid. On either side of the cylinder 1 one swinging arm or lever 5 swings about a pivotpin 4- fixed in the lower part of the cylinder 1, preferably at its lower end. These swinging arms or levers are provided near their upper ends with pivots 6 to allow gripping devices 7 to turn thereon. Each grip ping device 7 consists of a continuous rigid body about the length of the table or die and is provided with clamping members, later to be described. Pivot pins 8 are arranged on the bottom side of each gripping device 7, each pin 8 pivotally engaging one end of a telescopic press cylinder 9 actuated by pressure fluid, and pivoted with its other end on pivot pins 10 in the upper part of the cylinder 1. The telescopic press cylinders of one gripping device can be operated independently of each other by special control members, such as control valves, to permit the gripping devices to be adjusted to any desired position parallel or inclined to a work table 3 carrying the forming die. The left side of Fig. 2 shows such an inclined position.

While Figs. 1-3 show each gripping device 7 resting clined position of the gripping devices to the table is obtained or eifected by delivery of pressure fluid to the telescope cylinder controlled by valves in known manner.

According to Figs. 5 and 6 each swinging arm or lever 5 is operated instead of by telescope cylinders by mechanically driven spindles 15,, 16. Four pivots 17 are mounted in the upper part of the press cylinder 1 in which the spindle guide 18 is suspended on gimbals or universally suspended. On each spindle guide 18 is fixed a casing 19 in which a revolvingly mounted spur wheel 20 is driven by an electric motor 21 over a pinion 22. The spindles 16, 15 are provided with an outside screw thread and guided through a central threaded boring of the spur wheels. The screwed spindles 15, 16 are arranged crosswise side by side acting on the pivot pins 8 of the gripping devices 7. Preferably, the pivot pins 8 are symmetrically located on the gripping devices. Each motor 21 is provided with a switch for 3 adjustment of the gripping devices to any desired position parallel or inclined to the work table. The press plate construction used in this embodiment is described in Figs. 7 and 8.

The press according to Figs. 7 and 8 contains only one central press cylinder 25. The press table rests on a single hydraulic piston 24 longitudinally displaceable and turnable in the cylinder 25. The table 23 is pivotally connected to a plate 27 by means of a joint 26 provided at one end of the table. On this plate 27 is positioned the forming die 65 (Figs. 5, 6). To the opposite side of the press table 23 is fastened an auxiliary cylinder 28 in which a hydraulic piston 29 is arranged to cooperate with the bottom side of the plate 27. This auxiliary cylinder 28 is connected to a pressure pump 32 by means of a high pressure hose with a control valve 31. As illustrated in Fig. 8 the press table can be turned with the plate 27 around the axis of the piston 24 changing from the position indicated in full lines into the position 27a indicated in dotted lines. Jaws or grippers 33 are displaceable as indicated by arrow 34. According to the invention these jaws 33 can be arranged on swinging arms, or in the manner known hitherto. It is obvious that the table can be used in itslongitudinal adjustment (indicated in full lines in Fig. 8, and by dotted lines in Fig. 6) as well as in its transverse adjustment 27a (indicated in dotted lines in Figs. 5 and 8).

Figs. 9-11 show gripping devices having a continuous body and continuous gripping jaws extending over the whole length of the table or die, applicable to presses according to Figs. 1-8. Each gripping device has two gripping or clamping jaws 35, 36 between which the sheet metal to be treated is clamped tight with its edges by means of a key 37 extending over the whole length of the jaws. Fig. 9 shows a gripping device'having a U-shaped body in cross section between the two rectangular outer flanges 38, 39 of which the gripping jaws 35, 36 are keyed, the key being displaced in its longitudinal direction. The key 37 touches the outer flange 39,. It is driven into the gripping device, thereby pressing together the jaws 35, .36. between which the sheet metal is positioned.

Each key 37 is pressed intothe gripping device in its longitudinal direction by means of a hydraulically actuated piston 40. This piston 40 sliding within a cylinder 41 is pressed against the kcy3'7 by means of a pressure fiuid'from a source 42, such as a pressure pump, connected to the cylinder 41 by means of a flexible highpressure hose 43 and a valve 44.

Fig. 10 shows the body 45 of a gripping device provided with a longitudinal groove, the inner surfaces 48, 49 of the side flanges 46, i7 tapering upwardly. In this groove are arranged two key shaped gripping or clamping jaws 50, 51 and beneath them a key 52f As soon as the key 52 is pressed into the groove in its longitudinal direction the jaws 59,51 are forced upwardly clamping the sheet positioned between them. The surfaces 54, 55 facing the sheet 53 have a zigzag or undulated shape securing a tight clamping of the sheet. The key 52 is tapered along its length, and the jaws 50, 51 increase in height.

As shown in Fig. ll the sheet 53 is clamped between the flange 5,6 of the body 57 of the gripping device and the jaw 59. In the groove of the gripping device according to Fig. 11 only one clamping jaw and one key are arranged. The inner surfaces of the flanges 56, 58 are provided with one step securing gripping jaw 59 and key 60 in their right position. The surfaces 61, 62 of the flange 56 and of the gripping jaw 5b facing the sheet metal are rough to secure a tight clamping of the sheet. The key 60 is tapered along its length and; thejaw 59 enlarges correspondingly. The keys 52 and 60 are hydraulically driven into the, gripping device in their; longitudinal direction, as indicated in Fig. 9.

' a vertical pull is exerted The clamping or gripping jaws are preferably exchangeable and extend over the whole length of the Work piece or table. If two clamping jaws are arranged in the groove according to Fig. 9, these exchangeable jaws can be provided with a joint between the surfaces facing the sheet curved corresponding to the curved shape of the work piece. The use of divided grippers is avoided, they cause the sheet to tear easily at the edges of a single gripper. A further advantage of curving the clamping jaws is achieved when their shape corresponds to the curve of the finished work piece, thus a premature tear-off of the sheet is avoided. The operation of the new gripping devices requires much less time than hitherto and, moreover, sheet metal is saved as the sheet can be gripped or clamped closer than hitherto and only slight waste of sheet occurs at its edges.

The new drawing and stretching device according to the invention is adapted with advantage for forming fiat shaped parts, such as fiat motor car doors or flat roof parts of motor cars. The arrangement of the gripping devices on swinging arms of considerable length causes said devices to perform a flat arclike downwardly directed movement, so that the horizontal pull caused during the stretching process simultaneously receives a change in the downward direction and the sheet is drawn over the form of the die, thus wrapping it. This arelike movement results in a combined horizontal and vertical pull. As the gripping devices form the outer circumference of the press, the work piece is accessible from all sides for treating the sheet by hand after its shaping on the press. Bending stresses are very low as the pressure actuated members immediately act on the gripping devices.

By employing of a single press cylinder with a turn able piston carrying the press table and by arranging an inclined adjustable plate, an essentially simplified construction is achieved compared with those, known hitherto, which require a plurality of press cylinders for their longitudinal and transverse, and simultaneously inclined adjustment of the table.

The press is operated as follows:

After adjustment of the gripping devices to the desired position parallel or inclined to the table corresponding to the shape of the blank, and after positioning of theforming die on the table, the blank is laid over the die and clamped with its edges into the gripping devices. The power driven members are forced outwards, whereby said members can be controlled independently of each other by control members, such as control valves or switches, already known. The new device has the great advantage that when flat forms are used, no rise of the table is required but only the swinging arms must be forced away from the tool, as simultaneously with the horizontal pull and the die is entirely wrapped. After stretching and shaping the work piece can be finally finished by hand on the press. It the curvature of the die or the form of the work piece requires, the table can be moved upwardly.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A drawing and stretching press for sheet metal comprising a column provided with an axial bore, a work table, a piston having one end connected to said work table and another end extending into said bore of said column, means for longitudinally displacing said piston relative to said column, a plurality of levers having upper and lower ends, means pivotally connecting said lower ends of said levers to said column, means for gripping said sheet metal when disposed on said work table, said gripping means being operatively connected to said upper ends of said levers, respectively, and means for moving said levers and gripping means toward and away from said work table, said moving means being supported by said press in, a position between said levers and pivotally connected to said levers adjacent their upper ends, re-

spectively, whereby upon selective actuation of said moving means the respective lever is pivoted and the respective gripping means describes an arcuate movement.

2. A drawing and stretching press for sheet metal according to claim 1, wherein each of said moving means includes a cylinder and a hydraulically operated piston pivotally secured to said column and said lever arm, respectively, whereby upon actuation of said hydraulically operated piston movement of said lever arm results.

3. A drawing and stretching press for sheet metal according to claim 1, wherein each of said moving means includes a spindle having one end connected to a respective lever arm and having its other end threaded, a threaded support carried by said press through which support said threaded end of said spindle extends, and means for rotating said spindle relative to said threaded support, whereby said spindle is advanced through said support and said lever is pivoted relative to said column.

References Cited in the file of this patent UNITED STATES PATENTS 2,006,468 Longren July 2, 1935 Salzmann June 17, Oeckl Jan. 13, Berliner Apr. 14, Summers Feb. 22, Flowers Apr. 11, Lermont June 19, Lindsey Mar. 2, Lermont May 18, Martin Dec. 28, Nielsen Jan. 11, Maize July 19, Gray Mar. 24,

FOREIGN PATENTS Germany Nov. 6, Great Britain Sept. 26, 

